The present invention relates to connecting electrically and, positively mechanically, two tube systems to each other, each system being comprised of at least two concentric metal tubes separated by a synthetic layer. And more particularly the invention relates to interconnecting two tube systems to be used for the power supply of electrically driven underwater pumps.
It has been suggested to provide underwater pumps with electrical energy as well as with a coolant and lubricant through a conduit system which is comprised of three concentric tubes. These tubes are made of metal, but are insulated electrically with respect to each other. These three concentric tubes provide for conduction of electrical voltage and current of a three phase system so as to supply an underwater pump with three phase electric power and energy. The interior of the innermost tube serves as duct for the coolant and lubricant. Such a three tube conduit is disposed inside a somewhat larger tube, and the annular space between the three phase tube system and the last mentioned larger tube serves as return path for the coolant and lubricant. Basically, such a system is a rigid one, and the components, so to speak, are transported at finite length to an installation site where they have to be interconnected.
The connection must meet very high and stringent requirements. First of all, there must be positive connection between the individual tubes so that from a mechanical point of view they constitute a unit. Moreover, it is necessary that the electrical connection between tubes of similar diameter, i.e., similar relative disposition within the system is established positively with no appreciable electrical resistance being effective across the joint. Of course it has to be prevented that the joint in between two such tube systems can become for some reason or another a source for a short circuit. On the other hand, the interconnection of two tube systems must not be a permanent one. Rather, the connection has to be fairly easily releasable, because in the case of a defect, for example of the underwater pump, the pump has to hauled to the surface, which of course means that one has to retract the supply line. Since, as stated, the supply line is a rigid one, the individual sections have to be disconnected. On the other hand, connecting and reconnecting such tube sections to each other should not be a complicated affair, but be effected rather easy.